South Africa marked Nelson Mandela's 89th birthday on Wednesday with tributes and congratulations as the anti-apartheid icon prepared to launch a new international group to help solve the world's problems.

Mandela was to unveil the group of elder statesmen including former United States president Jimmy Carter, former United Nations secretary general Kofi Annan and former Irish president Mary Robinson at a news conference in Johannesburg.

"Nelson Mandela's role in this was to help bring the group together. What he will do today is introduce them to the media and to the public, bless them, and let them carry on with the work," Nelson Mandela Foundation head Achmat Dangor told South African Broadcasting Corporation radio on Wednesday.

Dangor said the new group would tackle pressing world issues, but that Mandela himself -- who stepped down as South Africa's president in 1999 and officially retired from public life in 2004 -- would not play a major role.

"Not only does he not have the time to devote to such a very complicated process, but we also think that his priorities should lie in Africa," he said.

Aides say Mandela is in good physical health for his age, and that he is spending his retirement quietly devoting time to his large family and wife Graça Machel, whom he married on his 80th birthday in 1998.

South African newspapers were full of well-wishes for the man who -- more than a decade after he won the first all-race elections that buried apartheid -- remains affectionately known by his clan name "Madiba" to South Africans across all racial lines.

"Madiba takes the cake" the Star newspaper said, running page after page of tributes and congratulatory messages from its readers.

A new poll released to coincide with the birthday showed Mandela's popularity in South Africa has actually grown since he stepped down as president.

The Markinor poll said Mandela scored an average rating of 9,2 out of 10 among some 3 500 people surveyed, "making him the country's most beloved leader".

The survey marked an improvement over Mandela's rating at the end of his presidency, which was about 8,2 out of 10, the results showed.

'Country and the world are privileged'
Mandela's birthday was also to be marked in Cape Town on Wednesday with a special soccer game between African soccer stars and a selection of great world players.

Meanwhile, President Thabo Mbeki wished Mandela a happy birthday.

Mbeki on Tuesday said the celebration of Mandela's birthday was an opportunity to "re-dedicate ourselves to the ideals and values for which he has stood and continued to uphold".

He said the soccer match was a fitting tribute to a deserving elder.

Mandela was an inspiration to South Africa, the continent and the rest of humanity through his life, his leadership, and his resolute and deep-seated commitment to the struggle against apartheid and for a just and democratic society.

"The country and the world are privileged to celebrate the life of such an outstanding leader of our people," wrote Mbeki in a statement.

Mbeki recalled Mandela's statement from the dock in the Rivonia Trial in 1964 when he said: "I have fought against white domination, and I have fought against black domination. I have cherished the ideal of a democratic and free society in which all persons live together in harmony and with equal opportunities.

"It is an ideal which I hope to live for and to achieve. But if needs be, it is an ideal for which I am prepared to die." - Reuters, Sapa